With a budget of some $4.5bn and 34,500 officers, the NYPD is by far the largest police department in the US, employing as many officers as the next four largest American cities combined. Size is not its only unique feature. The NYPD is part local police force and part intelligence agency, operating America's only city-level autonomous counterterrorism and intelligence operation, with a $100m budget and 1,000 employees.

New York City has seen dramatic drops in crime and has been spared a successful terrorist attack for more than a decade. But given the extent and the breadth of its activities across New York and beyond, it's no surprise that some of the NYPD's policies and practices have come under fire.

The two main sources of friction are the fact that African-American and Latino men are six times more likely to stopped and frisked by police than Caucasians, and the monitoring of Muslim neighborhoods without any suspicion of criminal and terrorist activity. Minority communities are visibly and volubly upset, with a major protest march planned for Father's Day this Sunday. Their dissatisfaction undermines the NYPD's ability to do its job: decades of research show that perceptions of police legitimacy influence the willingness of communities to co-operate with officers.

Unlike other American cities, New York's police set their policies without much civilian oversight. The police commissioner reports to the mayor, but operates with a high level of independence. In other cities, Los Angeles for example, a civilian commission sets policing policy. It relies on an independent inspector general to ensure full information about what's going on inside the police department.

When it comes to intelligence operations, America's top agencies – including the FBI and the CIA – have operated for decades under a system that includes an independent inspector general and regular, ongoing reporting to Congress. Indeed, as Congress has increased intelligence authorities after the attacks of 11 September, it has augmented oversight of how these new powers are used and their impact on civil liberties.

In New York, however, there is no oversight body that monitors the police to ensure that their policies and practices comply with local, state, or federal legal standards. The bodies that are even nominally charged with supervision are either weak, lack jurisdiction, have no independence, or all of the above. The NYPD's internal affairs bureau comes under the supervision of the police department itself. The mayor's commission to combat police corruption has no power to compel the police to provide witnesses or documents. The civilian complaint review board hears complaints by the public only against individual police officers. Meanwhile, the city's department of investigation has inspectors general for 300 city agencies, but not one for the NYPD.

The City Council has started taking seriously its responsibility to oversee the Police Department's policies and practices. In order to fulfil this responsibility and, indeed, to help New York's Mayor Michael Bloomberg do the same, the council needs a neutral and independent person – that is, an inspector general – examining police policies and practices. The inspector general could bring greater transparency to the traditionally closed worlds of policing and intelligence by developing and sharing reliable information. This would allow elected leaders and New Yorkers to better evaluate police activity and hold the police accountable. Acting as an honest broker, the inspector general could even help restore the fractured trust between the NYPD and minority communities, and lead to a stronger, more effective police force.

History has shown, time and again, that government operates best when it can be held accountable. This is especially true of police departments, whose activities have enormous impact on our daily lives, and of intelligence agencies that operate in secret. It's time New York took the first step in securing an accountable NYPD by creating an inspector general to review police operations and report regularly to the council and the mayor.